Wellbores are drilled through subsurface formations to extract useful fluids, such as hydrocarbons. Once drilled, a liner or casing with built in valves can be run-in-hole (RIH) and cemented in place. Hydraulic fracturing can then take place to create a path of fluid communication from a zone in the subsurface formation through the valves and into the casing.
Oftentimes, a single wellbore will have multiple zones to be fractured. One conventional method for fracturing multiple zones involves a bottom-up approach where a lowermost zone is fractured first, and zones closer to the surface are subsequently fractured. To accomplish this, a shifting tool is lowered to a point proximate the valves in the lowermost zone. The shifting tool is adapted to engage and open the valves with an upward motion. Once opened, fracturing can take place in the lowermost zone. The shifting tool can then re-engage and close the valves with a downward motion.
When the shifting tool is lifted above the lowermost zone to begin the fracturing process in a higher zone, the upward motion of the shifting tool tends to engage and re-open the valves in the lowermost zone. This is undesirable, however, as only the valves in the zone to be fractured should be in the open position during the fracturing process. What is needed, therefore, is an improved system and method for fracturing multiple zones in a wellbore.